Prokaryotic and eukaryotic cells responde to environmental stress by the induction of a variety of stress-related proteins. In mammalian cells, the most well characterized group of stress proteins are induced by hyperthermia. Transcription of heat shock proteins increases markedly after hypertherima and several of these genes have been cloned from Hela cells in other laboratories. It is likely that transcription of other genes is also induced in mammalian cells since approximately 10-20 genes are induced in prokaryotes and lower eukaryotes. One approach to isolate such transcripts is to enrich for heat shock specific cDNA's by hybridization subtraction with mRNA from control cells. We have done this with rodent cells, V79. We are currently constructing a cDNA library with this enriched cDNA. The eventual aim is to characterize the response of V79 cells to hyperthermia.